The proposed research will focus on the mechanisms by which electrical activity coordinates the surface expression of the A-type potassium channel Kv 4.2 hippocampal neurons. These channels are important in controlling the membrane excitability of the dendrite, a critical factor for normal physiological and pathological processes such as the initiation of long term potentiation (LTP), long term depression (LTD) and seizure. The regulation of the surface expression of Kv 4.2 potassium channels under conditions that promote or block synaptic activity will be addressed by the following specific aims: 1. Determine if a change in synaptic activity effects the surface expression of the A-type potassium channel Kv 4.2 in hippocampal neurons. 2. Determine the molecular mechanism for the change in activity- dependent surface expression of Kv4.2 These experiments are designed to explore how Kv4.2 channels are involved in feedback mechanisms that occur when a neuron undergoes changes in synaptic input during physiological processes such as development, learning, and memory.